Also, this comment a month ago on Quora:
We just did a Startup Weekend and instead of pitching ideas, attendees pitched problems. So much more enlightening. Almost twice the amount of pitches compared to a standard Startup Weekend.
This “problem first” approach has been part of the dialog on lean entrepreneurship at least since 2009 (see the date on the Dave McClure blogpost above.)

WHAT MAKES FLASHPOINT DIFFERENT?
Here’s what’s different:
If it’s true that you cannot rely on your reading of your customer’s rational self interest to predict their actions, then you don’t really know what constitutes a problem for them. Therefore, you can no more rely on your ability to assess the validity of a problem than you can rely on your ability to assess the value of a product idea – they are both equally mysterious until your do the work to suss them out.
Moral: You can’t reduce market risk by starting with a problem rather than a product. You can only reduce market risk by doing the work to reduce market risk. Where you do that work isn’t in the domain of a solution or a problem. Maybe it’s just in the domain of something you know about, want to work in, and bring valuable skills to.